This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled Cathode Ray Tube with Reduced Moirxc3xa9 earlier filed in the Korean Industrial Property Office on Jan. 28, 2000, and there duly assigned Serial No. 4372/2000 by that Office.
1. Field of the Invention
The present invention relates to cathode-ray tubes (CRTs), and more particularly to color cathode-ray tubes of a type having shadow masks effective in minimizing the moirxc3xa9 effect.
2. Description of the Background Art
A predominant number of color cathode-ray tubes in use today have shadow masks that include apertures of a circular type or a slot-shaped type. The apertures are aligned in columns along the minor axis of the shadow mask, or in a vertical direction, and the adjacent apertures in each column are separated from each other by bridges.
When the electron beams scan in an interlacing mode or a progressive mode, they also have scanning pitches. A scanning pitch is the distance between adjacent scanning lines. Since the apertures in the shadow mask as well as the scan lines are periodic, the electron beams that pass through each aperture interfere with each other to cause a disturbing effect which is the so-called moirxc3xa9 effect. This effect causes light and dark lines or lines of a deviating color in the image to deteriorate the qualities of the display images.
To overcome the moirxc3xa9 effect, a number of solutions have been proposed. For example, the vertical pitches of the apertures may be adjusted when designing a shadow mask. That is, since it is well known that the moirxc3xa9 effect seldom occurs when the wavelengths of moirxc3xa9 patterns are less than 2 mm (millimeters), the aperture pitches can be designed to minimize the moirxc3xa9.
However, the proposals to minimize the moirxc3xa9 effect are mainly developed for cathode-ray tubes such as television receivers with a NTSC (National Television System Committee) or PAL (phase alternation line) system. Efforts for eliminating the moirxc3xa9 effect have not been developed for cathode-ray tubes such as high-definition television (HDTV) systems. High-definition televisions generally have higher picture resolution than the PAL or NTSC systems.
Exemplars of the art are U.S. Pat. No. 5,861,710 issued to Uchida et al. for Color Cathode Ray Tube with Reduced Moire, U.S. Pat. No. 5,959,414 issued to Yoshida et al. for Moire Reducing Apparatus, U.S. Pat. No. 5,247,933 issued to Beeteson et al. for Moire Interference Detection for Raster-Scanned Cathode Ray Tube Display, U.S. Pat. No. 5,430,502 issued to Yamazaki et al. for Apparatus for Eliminating Moire Pattern Effects Resulting from the Use of Different Display Resolution with a Fixed Size Shadow Mask, U.S. Pat. No. 5,777,441 issued to Yoshida et al. for Moire Reducing Apparatus, U.S. Pat. No. 5,619,094 issued to Vriens for Color Cathode Ray Tube and Display Device with Reduced Moire, U.S. Pat. No. 5,606,216 issued to Uchida et al. for Color Cathode-Ray Tube with Reduced Moire, U.S. Pat. No. 4,638,212 issued to Nakaimura for Color Cathode-Ray Tube, U.S. Pat. No. 5,378,959 issued to Mancini for Shadow Mask Type Color Picture Tube with Reduced Moire, U.S. Pat. No. 5,055,736 issued to Yun et al. for Shadow Mask for Use in a Three-Gun Color Picture Tube, U.S. Pat. No. 5,841,247 issued to Vriens for Cathode Ray Tube Display System Incorporating Same and Computer Including Control Means for Display System, U.S. Pat. No. 5,825,435 issued to Vriens et al. for Color Cathrode Ray Tube and Display Device, and U.S. Pat. No. 5,534,746 issued to Marks et al. for Color Picture Tube Having Shadow Mask with Improved Aperture Spacing.
In view of the prior art described above, it is an object of the present invention to provide a cathode-ray tube for high-definition televisions having a shadow mask that is capable of minimizing the moirxc3xa9 effect due to the relation between a scanning pitch of the electron beams and a vertical pitch of the apertures in the shadow mask.
It is another object to provide a cathode-ray tube that decreases image distortion while providing higher resolution of the image.
It is yet another object to provide a device for displaying variable images that is manufactured according to a predetermined relationship between apertures in a shadow mask as well as the scan lines in order to reduce deterioration of the image because of light and dark lines or lines of a deviating color in the image.
It is still yet another object to have a device for displaying variable images that can decrease image distortion and yet increase the image resolution.
To achieve this object, a device includes a panel, a phosphor screen being arranged on an inner surface of the panel, a funnel connected to the panel, having a deflection yoke assembly on an outer periphery thereof, a neck connected to the funnel, having an electron gun assembly disposed therein, and a shadow mask disposed inside the panel, the shadow mask having a plurality of apertures allowing electron beams to pass through.
A vertical pitch Py between each of the neighboring apertures along a minor axis of the shadow mask and a scanning pitch Ps between each scan line of the electron beams satisfy the following relationship:
((2n+1)/4)xe2x88x920.1xe2x89xa6Ps/Pyxe2x89xa6((2n+1)/4)+0.1
where n is an integer not less than three.